Recently, a lot of companies consider making use of VOIP, because VOIP could save a great deal of telephone bills. Please refer to FIG. 1. It illustrates a flowchart of using VOIP according to the prior art. As shown in FIG. 1, an IP address corresponds to a telephone number. Dialing the telephone number is equivalent to a connection of the IP address to the Internet. Next, a voice is compressed by software for convenience of transmission via the Internet, which the compressed voice is digitalized. The compressed and digitalized signal could be transmitted to a receiver via IP-to-IP communication and then decompressed into a voice. Thus, the communication is established. That is a basic principle of VOIP according to the prior art.
The current VOIP has two communicating types as shown in FIGS. 2A and 2B. FIG. 2A illustrates a communicating type of peer-to-peer, wherein the communication is established merely via an application program in peer-to-peer manner. Generally, this method only introduces an Internet connection fee without any extra expenses. Presently, there are a lot of freeware programs available, such as SKYPE®. However, a user of this communicating type could communicate with another user only when these two users use the same application program. Such a user could not communicate with mobile phones or fixed telephones directly. FIG. 2B illustrates another VOIP communicating type. The user can be connected to another IP phone via a VOIP server, and the server is further connected with a switch, such that the IP phone can communicate with an external client user, such as fixed phone user or mobile phone user. Therefore, the user could communicate with any phone user. However, the user has to pay the service provider.
On the other hand, the prior art VOIP needs the cost of initialization. Furthermore, the quality of the Internet communication is not stable all the time. Moreover, there is a compatibility problem between a caller and a receiver—they should use the same application program or connect to the same service provider for communication. Therefore, the VOIP could not be popularized rapidly. Certainly, improving the bandwidth of network and developing new application programs could solve those problems.